1.2 kg watermelon (about ½), flesh removed with a melon baller75 gm (1/3 cup) caster sugarScraped seeds of ½ vanilla bean400 gm boysenberries or mulberriesTo taste: sparkling shirazWatermelon and boysenberry granita500 gm frozen boysenberries300 gm caster sugar1.3 kg watermelon (about 1/3 watermelon)
For watermelon and boysenberry granita, combine boysenberries and sugar in a heatproof bowl placed over a saucepan of simmering water, cover with plastic wrap and cook until mostly liquid (1 hour). Strain through a fine sieve, pressing lightly on solids to yield 400ml liquid, then refrigerate until chilled (1 hour). Meanwhile, blend watermelon in a blender until liquid, then strain through a fine sieve, pressing lightly on solids to yield 1 litre juice. Combine boysenberry syrup with watermelon juice, then freeze in a large shallow tray, scraping with a fork every few hours, until completely frozen (6 hours-overnight).
Combine watermelon balls, sugar and vanilla in a bowl and refrigerate until sugar dissolves (1 hour).
Place chilled watermelon and berries in chilled bowls, pour over a little sparkling wine to taste, top with granita and serve.